WO2008046754A2

WO2008046754A2 - Mechanical stopper and method for transporting substrates in automatic placement machines

Info

Publication number: WO2008046754A2
Application number: PCT/EP2007/060644
Authority: WO
Inventors: Robert Conrad; Mohammad Mehdianpour; Werner Pfaffenberger; Stefan Dietrich; Hans Jürgen MAYER; Bernd Zimmermann
Original assignee: Siemens Aktiengesellschaft
Priority date: 2006-10-19
Filing date: 2007-10-08
Publication date: 2008-04-24
Also published as: WO2008046754A3

Abstract

The invention relates to a substrate transport device (100), comprising a transport device (2) for transporting substrates (1, 32) in a direction of transport (x) of a transport plane (x-y) to a placement area (6) of a placement head (20), and at least one mechanical stopper (10, 30, 40) that has a protrusion (43) and can be displaced between a first position (P1) and a second position (P2). The invention is characterized in that the protrusion (43) stops the transport of the substrates (1, 32) in the first position (P1) and allows the transport of the substrates (1, 32) in the second position (P2), wherein the second position (P2) of the protrusion (43) relative to the transport plane (x-y) is located on the side of the placement head (20) and the first position (P1) can be adjusted to different distances from the transport plane (x-y).

Description

description

Substrate transport device, placement machine, mechanical stopper and method for transporting substrates in automatic piece machines

The invention relates to a substrate transport device with a transport device for transporting substrates in a transport direction of a transport plane to a placement region of a placement and at least one mechanical stopper having a projection which is movable between a first and a second position, wherein the projection in the first position stops the transport of the substrates and in the second position allows the transport of the substrates, on a placement machine, on a mechanical stopper for use in a substrate transport device with a projection which is movable between a first and a second position wherein the projection in the first position stops the transport of the substrates and in the second position allows the transport of the substrates and on a method for transporting substrates in a placement machine.

Substrates, in particular printed circuit boards, which are to be loaded in a placement machine, are transported to the placement machines by means of transport devices, for example driven conveyor belts arranged laterally on a transport path. For stopping the substrates in a placement area mechanical stoppers are used inter alia. After stopping and fixing the substrates, they are equipped with components using a placement head of the placement machine, wherein the placement head moves in the direction of the substrates during a settling movement. The currently used mechanical stoppers sit between the two conveyor belts below the transport plane. This results in the following restrictions for the placement machines, especially in the placement area: The free space under the substrate is limited if a stopper is positioned in the area of a lifting table for a printed circuit board support.

- The position of pins for PCB support on the lift table is only limited selectable. It is limited by the space of the usual stopper.

- A stopper can be positioned only to a limited extent in the area of the lifting table if vacuum-actuated, freely displaceable pins which support the printed circuit boards are used.

The mechanical stoppers are mounted in the transport path of the substrates under the substrates and are pneumatically extended. The position for such a stopper is very limited. The occurring strokes are large, as under a circuit board substrate as a clearance of 40mm must be maintained.

Furthermore, it is known to recognize by means of light sensors or light barriers incoming printed circuit boards as substrates and then to stop the drive of the conveyor belts.

By US6256896 B, a mechanical stopper is also known, which can be pivoted by means of a compressed air cylinder from above into the transport path of the substrates in a fixed stop position.

It is the object of the invention to provide a substrate transport device, a placement machine, a mechanical stopper and a method for transporting substrates in a process. Specify piece machines, which offers more applications and above all a simpler way to stop multiple substrates in a placement area.

The object is achieved by a substrate transporting device of the type mentioned above with the characterizing features of claims 1 and 7, by a placement with the features of claim 9, by a mechanical stopper of the type mentioned above with the characterizing features of claim 10 and by a Method with the features of claim 18.

In this case, the second position of the projection with respect to the transport plane is located on the side of the placement and thus the projection stops the substrates in common placement machines, in which the placement is located above the substrates, from above. Thus, no device between the transport cheeks of a transport device is more necessary. Due to the adjustability of the first position, the stopper can be adapted to different substrate thicknesses. This can be done in a simple manner by a controllable stopper drive without manual intervention from the outside. The stopper can be kinematically fixedly coupled to the guide element according to claim 7, so that both can be actuated by a common drive, wherein the stopper and the guide element can be combined to form a component.

The mechanical stopper according to claim 10 represents a compact unit which, if necessary, can also be retrofitted to already completed placement machines or substrate transport devices. In the advantageous embodiment of the substrate transport device according to claim 2, the stopper pawl is outside of the placement area of the placement, which ensures that the placement is not limited in its movement during placement.

A particularly secure embodiment with regard to the avoidance of damage to the placement head is provided according to claim 3, characterized in that the stopper pawl is arranged in a side region of the transport path.

A transport device according to claim 4, which is designed as a conveyor belt driven in transport conveyor belt in a side region of the transport plane, below the substrate advantageously provides space for a lift table and possibly support pins for the substrates.

By attaching the mechanical stopper outside the transporting cheeks according to claim 5, the transport cheeks can be moved closer together and thus transported even narrow substrates and then assembled.

The arrangement of several mechanical stoppers in the transport direction in succession according to claim 6 or by the corresponding method according to claim 19 or 20, several substrates can be stopped in the placement and thus the Bestücknutzen be increased.

The transport device according to claim 7 advantageously effects that subsequent substrates can be approached abruptly against an already stopped substrate in the placement area, since this design of a very narrow gap between substrate and boundary surface of the stopper pawl prevents a subsequent the following further substrate can slide on an already stopped substrate. Due to the adjustability of the distance to the transport plane, the guide height can be optimally adjusted to substrates of different thicknesses. A correspondingly advantageous method is realized according to claim 21.

According to the advantageous embodiment of claim 8, the number of mechanical parts is reduced, since the Stopperklin- ke and the guide element formed on a part, operated together and can also be used as a clamping comb for the substrates.

The mechanical stopper advantageously has a suitable sensor according to claim 11 in order to signal the presence of a substrate to further mechanical stoppers. Subsequently, then further substrates can be retracted into the placement area and stopped by the other mechanical stoppers.

Due to the free positioning of the mechanical stopper according to claim 12 on the transport cheek adjustments with respect to the length of different substrates can be made in a simple manner.

A simple embodiment of the mechanical stopper results according to claim 13 by the interaction of a lifting cylinder and a return spring for moving the stopper pawl.

By the rotational movement according to claim 14 can be realized fast switching times. The range of movement of the placement is not impaired according to the advantageous embodiment of the mechanical stopper according to claim 15, characterized in that the lever is formed thinner in the direction transverse to the transport direction.

In the advantageous embodiment of the method according to claim 22, the substrates can be separated again after loading.

Based on embodiments shown in the figures of the drawing, the invention will be explained in more detail.

Show

1a shows a schematic cross section through part of a substrate transport device according to the invention with a first embodiment of a mechanical stop when stopping two substrates,

1b is a schematic diagram in side view of the first embodiment as a section along the line A-A 'of Fig. Ia when stopping two thick substrates,

1c shows a schematic diagram in side view of the first exemplary embodiment as a section along the line A-A 'of FIG. 1a when stopping two thin substrates, FIG.

2a shows a schematic cross section through the part of the substrate transport device according to the invention with the first embodiment of the mechanical stopper when clamping two substrates, 2b is a schematic diagram in side view of the first embodiment as a section along the line BB 'of Fig. 2a when clamping the two thick substrates,

2c is a schematic diagram in side view of the first embodiment as a section along the line B-B 'of FIG. 2a when clamping the two thin substrates,

3a shows a schematic cross section through the part of the substrate transport device according to the invention with the first embodiment of the mechanical stopper before a further transport of the substrates,

3b shows a schematic diagram in side view of the first exemplary embodiment as a section along the line C-C of FIG. 3a before the further transport of the thick substrates,

3c is a schematic diagram in side view of the first embodiment as a section along the line C-C of Fig. 3a before the further transport of the thin substrates,

4a shows a schematic cross section through part of a substrate transport device according to the invention with a second embodiment of the mechanical stop when stopping two substrates,

4b is a schematic side view of the second embodiment when stopping the two substrates,

Fig. 4c is a schematic diagram in side view of the second

Embodiment as a section along the line DD 'of Fig. 4a when stopping two thick substrates, 4d is a schematic diagram in side view of the second embodiment as a section along the line DD 'of Fig. 4a when stopping two thin substrates,

5a shows a schematic cross section through the part of the substrate transport device according to the invention with the second embodiment of the mechanical stopper when clamping two substrates,

5b shows a schematic side view of the second embodiment when clamping the two substrates,

5c is a schematic diagram in side view of the second embodiment as a section along the line E-E 'of Fig. 5a when clamping the two thick substrates,

5d is a schematic diagram in side view of the second embodiment as a section along the line E-E 'of Fig. 5a when clamping the two thin substrates,

6a shows a schematic cross section through the part of the substrate transport device according to the invention with the second embodiment of the mechanical stopper before a further transport of the substrates,

6b is a schematic side view of the second embodiment before the further transport of the substrates,

6c is a schematic diagram in side view of the second embodiment as a section along the line FF 'of Fig. 6a before the further transport of the thick substrates, 6d is a schematic diagram in side view of the second embodiment as a section along the line FF 'of Fig. 6a before the further transport of the thin substrates,

7 is a schematic plan view of a substrate transport device according to the invention with a plurality of stopped substrates,

8a is a first side view of a third embodiment of a mechanical stopper according to the invention,

8b is a second side view of the third embodiment of the mechanical stopper according to the invention,

Fig. 8c is an exploded view of the third embodiment of the mechanical stopper according to the invention.

In Fig. Ia is shown schematically in cross section a right part of a substrate transport device 100. In this case, a substrate 1, for example, an unpopulated or not yet fully assembled circuit board, in the placement area 6 of a placement (not shown) transported so that they can be equipped there with the help of a placement head 20 with components. In the illustrated construction, the placement head 20 would thereby place the components coming from above in the z-direction onto the substrate 1. Transport belts 3, which are guided as endless belts in a transport direction x about transport rollers 4 (see FIG. 1 b), which are arranged so as to be movable on a transporting arm 5 in a direction z perpendicular to the transport plane xy. A first exemplary embodiment of a mechanical stopper 10 with a lifting cylinder 11, a return spring 12 and a stopper pawl 13, which is connected to the lifting cylinder 11 via a connecting section 14. is, is connected via an assembly unit 15 (shown schematically) with the transport cheek 5. The stopper pawl 13 moves within a groove 17 of a terminal block 9. As a rule, the substrate 1 in the y-direction on the other side is also transported and held by an identically constructed conveyor belt 3 (as shown in Fig. 7). The two conveyor belts 3 together with the transport rollers 4 and the transport cheeks 5, the transport device 2. The distance of the transport cheeks 5 in the y direction can be adjusted for the transport of substrates of different widths 1. The assembly unit 15 is located outside a transport path, which is bounded laterally by the transport cheeks 5 and on which the substrate 1 is transported to the placement area 20. As a result, the transport of the substrate 1 and possibly also existing supports below the substrate 1 (eg support pins) are not hindered.

In the state shown in Fig. Ia, the lifting cylinder 11 is extended and presses the return spring 12. The stopper pawl 13 is lowered to a height of about 300 microns above the conveyor belt 3 and a projection 43 of the stopper 13 blocked in a first position Pl so Further transport of the substrate 1 in a side region 7 of the transport plane xy. About the connecting portion 14, the stopper pawl 13 is moved in the illustrated embodiment in the direction of the substrate 1 to. By the lowered stopper pawl 13, the retracted into the placement area substrate 1 is stopped. A subsequent further substrate 32 abuts on the already stopped substrate 1 and is also stopped e-.

FIG. 1 b shows in a side view a basic diagram for the stopping of two thick substrates 1, 32 and in the following. Immediately in Fig. Ic in a side view a schematic diagram for the stopping of two thin substrates 1, 32 shown. For different thick substrates 1, 32, the stopper pawl 13 and thus the projection 43 are lowered in different depths in the z direction in order to stop the substrates 1, 32 so that the further substrate 32 can not slide over the already stopped substrate 1.

In Fig. 2a is shown in schematic cross section, as the substrate 1 is clamped before the actual placement process. For this purpose, the conveyor belt 3 is moved on the transport cheek 5 in the z-direction upwards, so that the substrate 1 is pressed against a separate from the stopper pawl 13 terminal block 9 and thus clamped. The stopper pawl 13 and the projection 43 are not needed in this state, they are in the second position P2, the lifting cylinder 11 is retracted. Corresponding schematic schematic diagrams are shown in FIGS. 2 b and 2 c for thick and thin substrates 1, 32, which are clamped together on the clamping strip 9 separated from the stopper pawl 13.

In Fig. 3a it is shown that after the loading of the substrate 1, the conveyor belts 3 are moved along the transport cheek 5 in the z-direction down, the lifting cylinder 11 remains retracted, the stopper pawl 13 with the projection 43 is in the second position P2 and therefore no longer acts on the substrate 1, which can subsequently be transported out of the placement area 20 with the aid of the conveyor belts 3; FIGS. 3b and 3c show the associated schematic basic diagrams in side views for thick and thin substrates 1, 32 when two substrates 1, 32 were driven on impact. In FIG. 4 a, a substrate transport device 100 with a second exemplary embodiment of the mechanical stopper 30 is shown in schematic cross-section and in FIG. 4 b as a side view. The mechanical stopper 30 comprises a lifting cylinder 11 and a stopper pawl 13, which simultaneously acts as a clamping comb 19. In the pressureless state, the clamping comb 19 is pressed with the return spring 12 to the upper stop. Upon activation of the lifting cylinder 11, the return spring 12 is suppressed and the projection 43 of the stopper pawl 13 is lowered to a height of about 300 microns above the conveyor belt 3 and blocks the further transport of the substrate 1 and the subsequent further substrate 32. The height is by means of a Screw 16 set. The ratios for thick and thin substrates 1, 32 are shown in FIGS. 4c and 4d.

As shown in Figures 5a-5d, the conveyor belt 3 is pressed together with the clamping comb 19 in an upper position (for example, by a conventional, not shown, lifting table), wherein the clamping comb 19 is lifted by the lifting cylinder 11. In this position, the substrates 1, 32 are clamped against the clamping comb 19 and can be equipped by the placement head 20.

As shown in Figures 6a-6d, the conveyor belt 3 is lowered for extending the substrates 1, 32 (for example, by the lifting table, not shown), the clamping comb 19 remains in the upper position.

In Fig. 7 it is shown that in addition to a first mechanical stopper 10, 30, 40 in the transport direction x successively more mechanical stoppers 36 are arranged laterally of the transport path 8. Thus, in addition to a first substrate 1 further substrates 32 are stopped one behind the other become. The mechanical stoppers 10, 32 have light barriers 21 or other suitable sensors which respond to the presence of substrates 1, 32. If a stopped first substrate 1 is detected, the next further mechanical stopper 36 can lower another stopper pawl 31 with a further projection 34 in the side region 7 in order to stop a further substrate 32. The conveyor belt 3 continues to move. After retraction of the last further substrate 32, the conveyor belt 3 is stopped. All stop pawls 13, 31 are moved upwards. The lift table

(not shown) moves upwards and clamps all substrates 1, 32 with the aid of the clamping combs 19 of the mechanical stoppers 10, 36 and a clamping bar 9 located opposite in the y-direction. After the placement process by the placement head 20, all the substrates 1, 32 become simultaneously moved out the placement area 6. In narrow substrates 1.32 they can be separated by a successive raising or lowering of the stopper pawls 13, 31.

The stopper pawls 13, 31 can be designed so that they have an extension 18 in the transport direction x next to the projection 43 or the further projection 34, so that only a narrow gap remains between a substrate surface and the surface of the extension 18, the thinner as a substrate 1, 32. Thus, it is shown by way of example in FIGS. 1b, 2b, 3b, 1c, 2c, 3c. Thus, when loading a plurality of substrates 1, 32 in the placement area 20, additional mechanical stoppers 36 can be dispensed with. The narrow gap ensures that subsequent further substrates 32 can not slide over previously stopped substrates 1. The substrates 1, 32 are pushed on impact and then clamped together and populated by the placement head 20. The width of the gap can be adjusted by a corresponding movement of the stopper pawl 13 in the z-direction. The boundary surface of the extension 18 is offset in the direction z perpendicular to the transport plane xy by not more than a double substrate thickness to a boundary surface of the projection 43.

By the mounting unit 15, the mechanical stoppers 10, 30 are freely positioned on the transport cheek 5. For a flexible adjustment of the stop positions of the substrates 1, 32 is possible.

As shown in the figures, the mechanical stopper 10, 30 are outside the transport path 8, thereby the transport cheeks 5 can be moved closer together, and thus also narrow substrates 1 are fitted.

FIGS. 8a, 8b and 8c show a third exemplary embodiment of a mechanical stopper 40 in different views. 8a and 8b show two side views offset by 90 ° and FIG. 8c an exploded view.

Also, this mechanical stopper 40 is directly integrated with the transport cheek 5. The mechanical stopper 40 is designed in the form that it allows the substrate 1 to pass unhindered in the open position in the second position P2, but not higher than the existing transport cheek 5, to keep the distance or stroke of the placement 20 low ,

The stopper pawl is formed as a lever 42 with a small projection 43, the lever 42 is rotatably mounted about an axis 44, wherein a linear movement of a switchable solenoid 45 or other suitable schaltba- ren actuator is converted into a rotational movement. The stroke can be kept very low by the direct integration with the transport cheek 5.

Also, this mechanical stopper 40 can be integrated parallel to the lifting table and thus two or more mechanical stoppers 40 can be integrated into the transport cheek 5 to stop two or more substrates 1 defined in the placement area.

Due to the shape of the lever 42 and the special arrangement of the pivot point closing of the mechanical stopper 40 at an angle of only about 25 ° is possible. The height of the lever 42 becomes thinner towards the end in a direction y transversely to the transport direction x, so that no obstruction of the placement head 20 takes place in the second position P2.

The projection 43 is dimensioned in the z-direction so that very thin substrates 1 can be stopped, without affecting the freedom of movement of the still running conveyor belt 3 and dimensioned in the y-direction so that the projection is not in the Bestückbereich 6 of Placement head 20 engages.

The third embodiment of the mechanical stopper 40 can be easily integrated into the transport cheek 5. Due to the low necessary stroke a fast switching is possible. A small size is given and there is no increase on the transport cheek 5 addition.

All embodiments of the mechanical stoppers 10, 30, 40 can be used in the described substrate transport device 100 in an advantageous manner. Due to the good accessibility, these are easy to swap. you are variably positionable when the positions are provided in the transport cheek 5. Under the substrate, the free space is not restricted, the positions for support pins for the substrates are not limited and further options can be freely mounted on the lift table.

LIST OF REFERENCE NUMBERS

1 substrate

2 transport device 3 conveyor belt

4 transport roller

5 transport cheek

6 placement area

7 side area 8 transport route

9 terminal block

10 1st embodiment of the mechanical stopper

11 lifting cylinders

12 return spring 13 stop pawl

14 connection section

15 mounting unit

16 screw

17 slot in terminal block 18 extension

19 clamping comb

20 placement head

21 photocell

30 2nd embodiment of the mechanical stopper 31 further stopper pawl

32 additional substrate

34 further advantage

35 more photocells

36 further stopper 40 3rd embodiment of the mechanical stopper

41 stop pawl

42 levers

43 lead

44 Axis 45 Solenoid

100 substrate transport device

Pl first position

P2 second position X transport direction

Y direction transverse to the transport direction x-y transport plane z direction of movement of the transport cheek

Claims

claims

A substrate transport device (100) with a transport device (2) for transporting substrates (1, 32) in a transport direction (x) of a

Transport plane (xy) to a Bestückbereich (6) of a placement head (20) and with at least one mechanical stopper (10, 30, 40) having a projection (43) between a first position (Pl) and a second Position (P2) is movable, wherein the projection (43) in the first position (Pl) stops the transport of the substrates (1, 32) and in the second position (P2), the transport of the substrates (1, 32) permits the second position (P2) of the projection (43) with respect to the transport plane (xy) on the side of the placement head (20) is arranged, characterized in that the first position (Pl) at different distances to the transport plane (xy) is adjustable.

2. substrate transport device (100) according to claim 2, characterized in that the projection (43) outside the Bestückbereichs (6) of the placement head (20).

3. substrate transport device (100) according to claim 2, characterized in that the projection (43) in the first position (Pl) in a parallel to the transport direction (x) extending side region (7) of the transport plane (x-y) is located.

4. substrate transport device (100) according to claim 3, characterized in that the transport device (2) as transport wheels (4) driven conveyor belt (3) in a side region (7) of the transport plane (xy) is formed.

5. substrate transport device (100) according to one of claims 1 to 4, characterized in that the transport device in the transport direction (x) over a width of the substrate (1) forms a transport path (8) that the mechanical stopper (10, 30, 40 ) has an assembly unit (15) and that the mounting unit (15) outside the transport path (8) is mounted.

6. substrate transport device (100) according to one of claims 1 to 5, characterized in that in the transport direction (x) one behind the other a plurality of mechanical stoppers (10, 30, 40) is arranged.

7. substrate transport device (100) with a transport device (2) for transporting substrates (1, 32) in a transport direction (x) of a transport plane (xy) to a placement region (6) of a placement head (20) and with at least one mechanical stopper ( 10, 30, 40) having a projection (43) movable between a first position (Pl) and a second position (P2), the projection (43) in the first position (Pl)

Transport of the substrates (1, 32) stops and in the second position (P2) the transport of the substrates (1, 32) permits, characterized in that the projection (43) in the direction opposite to the transport direction (x) a perpendicular to the transport plane movable guide element for at least one of the substrates (1, 32) adjoins the substrate (1, 32) facing the boundary surface at different distances to the transport plane (xy) is adjustable.

8. substrate transport device (100) according to claim 7, characterized by the guide element as an extension (18) of the projection and is additionally formed as a clamping comb (19) which, after assembly of the mechanical stopper (10, 30, 40) in the substrate transport device (100) serves to clamp the substrates (1, 32) during loading.

9. placement machine with a substrate transport device (100) according to any one of claims 1 to 6 and with a placement head (20) for placing components on the substrate (1, 32).

10. Mechanical stopper (10, 30, 40) for use in a substrate transport device (100), which substrates (1, 32) in a transport direction (x) of a transport plane (xy) to a placement region (6) of a placement head (20) and having thereto a transport device (2), with a projection (43) which is movable between a first position (Pl) and a second position (P2), wherein the projection (43) in the first position (Pl ) stops the transport of the substrates (1, 32) in a transport direction (x) of a transport plane (xy) and in the second position (P2) allows the transport of the substrates (1, 32), the second position (P2) of the projection (43) with respect to the transport plane (xy) on the side of the placement head (20) is arranged, characterized in that the mechanical stopper (10, 30, 40) has a mounting unit (15) which is formed so that after assembly in the substrate transport device (100) the first pos ition (Pl) is adjustable to different distances to the transport plane (x-y).

11. Mechanical stopper (10, 30, 40) according to claim 10, characterized by a sensor (21) for detecting the presence of a substrate (1).

12. Mechanical stopper (10, 30, 40) according to any one of claims 10 or 11, characterized in that the mounting unit (15) as on a transport cheek (5) of the transport device (2) is freely positionable.

13. Mechanical stopper (10, 30, 40) according to any one of claims 10 to 12, characterized by a lifting cylinder (11) for the execution of the movement and by a return spring (12), the projection (43) without applying a force holding the lifting cylinder (11) in the second position (P2).

14. Mechanical stopper (10, 30, 40) according to any one of claims 10 to 13, characterized in that the projection (43) is formed as part of a stopper pawl (13) and the stopper pawl (13) has a lever (42) um- which is rotatably mounted about an axis (44) and the movement from the second position (P2) to the first position (Pl) is a rotational movement about the axis (44).

15. Mechanical stopper (10, 30, 40) according to claim 14, characterized in that the lever (42) is designed such that after assembly of the mechanical stop (10, 30, 40) in the substrate transport device (100) in the direction ( y) is made thinner to the middle of a transport path (8) formed by the substrate transport device (100) than at the edge of the transport path (8).

16. Mechanical stopper (10, 30, 40) according to any one of claims 14 or 15, characterized in that the projection (43) in one direction (y) transversely to the transport direction is formed only so large that this is not in the placement area ( 6) extends.

17. Mechanical stopper (10, 30, 40) according to any one of claims 8 to 16, characterized by a switchable actuator (45) for driving the movement of the projection (43).

18. A method for transporting substrates (1, 32) in a placement machine in which the substrates (1, 32) by a transport device (2) in a transport direction (x) a transport plane (xy) to a Bestückbereich (6) of a Placement head (20) of the placement machine and the substrates (1, 32) by a projection (43) which is movable between a first position (Pl) and a second position (P2), wherein the projection (43) in the first Position (Pl) the transport of the substrates (1, 32) stops and in the second position (P2), the transport of the substrates (1, 32) permits, are stopped, wherein the second position (P2) of the projection (43) with respect Transport level (xy) on the side of the placement head (20) and wherein the first position (Pl) can be set to different distances to the transport plane (xy).

19. A method for transporting substrates (1, 32) in an automatic placement machine according to claim 18, characterized in that initially a first substrate (1) is transported to the placement area (20) and stopped by a first projection (43) and then at least one further substrate (32) transported to the placement area (32) and stopped by a further projection (34).

20. A method for transporting substrates (1, 32) in a placement machine according to claim 19, characterized in that the further substrate (32) in the transport direction (x) in front of the first substrate (1) is stopped.

21. A method for transporting substrates (1, 32) in an automatic placement machine according to claim 1, characterized in that initially a first substrate (1) is transported to the placement area (20) and stopped by a first projection (43) and then at least one further substrate (32) transported to the placement area (20) and stopped by the already stopped first substrate (1) and by an extension (18) on the first projection (43) and by the choice of the first position (Pl) is prevented the further substrate (32) slides over the stopped first substrate (1).

22. A method for transporting substrates (1, 32) in a placement machine according to one of claims 19 to 21, characterized in that by a successive movement of the first projection (43) and the further projections (34) from the first position ( Pl) in the second position (P2) after loading a separation of the substrates (1, 32) takes place.